The use of abrasive-laden fluid streams to treat teeth has long been known. For example, U.S. Pat. No. 2,661,537 to Angell describes equipment for treating teeth with a relatively high-pressure stream laden with abrasive particles. While the use of such equipment has gained a significant degree of success in connection with the cleaning of teeth, there has heretofore been an overall lack of success in the dental industry with respect to the use of such equipment for cutting, excavating or etching teeth. Applicant has found that this lack of success can be attributed to several heretofore unrecognized disadvantages associated with equipment of the type described in Angell.
For example, cutting or etching of teeth with gas/abrasive streams frequently requires a source of fluid at pressures of at least about 120 psig. Unfortunately, however, compressed air in the range of about 60 to 80 psig is generally the highest pressure available in dental operatories. In order to overcome this limitation, the Angell patent describes the use cylinders containing CO.sub.2 gas at a pressure of about 800 psig as a source of pressurized fluid. Applicant has found that there are numerous disadvantages associated with the use of pressurized gas in this form. For example, applicant has found that one important factor in achieving successfully cutting, etching and/or excavating tooth enamel is proper regulation and control of the pressure at which such operations are carried out. Such precise control and regulation is difficult to achieve in the system described in Angel. One reason for this difficulty is the very large pressure differentials between the pressure needed to operate the system (e.g. 100 to 120 psig) and the pressure at which the gas is delivered (800 psig). In particular, the accuracy of pressure regulation equipment is frequently inversely proportional to the pressure differential across the regulating device. Thus, the precision of the regulated pressure frequently decreases as the pressure differential increases.
Another disadvantage of the equipment described in Angell is that it is capable of providing only two pressure levels for the fluid utilized to operate the system. Applicant has found that this is another reason for the lack of success achieved by prior devices. It is highly desirable to operate at more than two distinct and different pressure levels because of the multiplicity of dental procedures performed by the dentist. The equipment described in Angell, however, is capable of supplying fluid at only two distinct pressure levels. As a result, the required precision in operating the dental instrument is deficient. Another disadvantage arises on account of the provision for the supply of gas in compressed form in cylinders. In view of the considerable volume of gas being used, cylinder replacement becomes a severe inconvenience. Thus, applicant has found that the use of equipment as described in Angell is a disadvantage in treatment operations involving the use of abrasive-laden fluid streams.
The prior art use of abrasive-laden fluid streams for treatment of teeth has also suffered from the disadvantage of having significant excess and/or post-use abrasive particles in the area of the mouth during operation. The presence of such abrasive particles is not only uncomfortable to the patient being treated, but it may also constitute a hinderance to the dentist conducting the operation. This disadvantage is particularly relevant for cutting and abrading of teeth since the relatively high pressures required for such operations sometimes result in a cloud or mist of excess or post-use abrasive particles which make it difficult for the dentist to see the area being treated. This difficulty has heretofore not been fully overcome.